7075 is a heat-treatable aluminum alloy that contains zinc, magnesium and copper as precipitation hardening solute elements. It has very high strength under static conditions in the T6 temper, but does not have corresponding high fatigue resistance. Its fatigue strength is comparable to that of the lower static strength 2024 and 2014. The loss of fatigue strength is thought to be due to the gradual decomposition of the hardened particles located in the slip zone, gradually reducing their size until they become unstable and dissolve into the substrate, thereby losing their hardening function.
The 7075-T6 temper has high susceptibility to stress corrosion cracking, especially in the short transverse direction (e.g. through the thickness of the plate). When this stress corrosion susceptibility is important to the product’s application, it can be improved using the proprietary T73 temper, at the expense of strength, which is approximately equivalent to that of the 2014-T6 alloy.
The first 7075 alloy was secretly developed by Japan’s Sumitomo Metal in 1935 and was standardized and used for aerospace purposes in 1945.
| Main composition | Zn | Mg | Cu | Cr | Al |
|---|---|---|---|---|---|
| 7075 | 5.6 | 2.5 | 1.6 | 0.3 | Balance |
| 7075composition (wt.%) | Min | Max |
|---|---|---|
| Cu | 1.2 | 2.0 |
| Mg | 2.1 | 2.9 |
| Mn | -- | 0.30 |
| Fe | -- | 0.7 |
| Si | -- | 0.50 |
| Zn | 5.1 | 6.1 |
| Cr | 0.18 | 0.40 |
| Ti | -- | 0.20 |
| Other impurities | ||
| each | -- | 0.05 |
| total | -- | 0.15 |
| Al | Balance | |
Mechanical properties：
| Alloy | T.S. (MPa) | Y.S. (MPa) | Elongation (%) | Density (gcm3) |
|---|---|---|---|---|
| 7075-T6 | 572 | 503 | 11 | 2.81 |
| 7075-T73 | 505 | 435 | 13 | 2.81 |
Application：
It can be used for general aircraft parts, missile parts, forging bars, worm gears and other products.
References：
1.AIWT, Aerospace Structural Metals Handbook, Nonferrous Alloys, 7075Al
2.Matweb, datasheet.
Standards：
AMS 4154、AMS4167、AMS4168、AMS4169
